Author Topic: identify this wire! (Read 3418 times)

irish44j · « **on:** December 23, 2012, 02:49:21 PM »

just finishing up my M42 swap into an M10 car. Engine is running, etc. I have mystery connector that comes off the harness near the DME main plug above the glove box. One wire is black with white stripe and the other is purple with white stripe.

I can't find this thing anywhere in the electrical troubleshooting manual or other wiring diagrams. I read one place that it has something to do with the tach, but not sure. Since my car had an M10 with K-Jet and is an '85 I don't have a connector in that area that matches up.....

Anyone know?

ak96ss · « **Reply #1 on:** December 23, 2012, 03:30:43 PM »

Are you sure they are white and not gray - as in BK/GY and VI/GY?

Possibly C136, HVAC connections - pages 6452-0 and 6452-1 in the ETM for the '91.

Just a stab in the dark...

irish44j · « **Reply #2 on:** December 23, 2012, 04:13:14 PM »

will take a closer look, but if they're gray, they're really faded. I'll look at my second harness too. Someone mentioned somewhere else that they might have to go to the gauge cluster for the tach. HVAC would make more sense, but of course I have A/C deleted...

DesktopDave · « **Reply #3 on:** December 23, 2012, 09:16:35 PM »

The tach plug is a lot smaller, rectangular in section and has three wires. I think it was called the C103 connector. It should be in all e30s before the wiring update in mid-'87(?). You should also have an idle control harness with a large green plug that was eliminated in later 1.3 versions of the Motronic system. Like others have mentioned, it must be spliced into the large motronic plug in order to make the tach functional.

I had two plugs very similar to that one on a '90 325i harness - one was white and the other was black. They didn't connect to anything. I've never know what they were for, figured it was for the stereo or some sort of OEM dealer-installable security system.

bmwman91 · « **Reply #4 on:** December 23, 2012, 11:38:37 PM »

I believe that that plug is for the 13 button OBC's CODE/lock-out function.

irish44j · « **Reply #5 on:** December 24, 2012, 11:27:05 AM »

Quote from: DesktopDave;118727

The tach plug is a lot smaller, rectangular in section and has three wires. I think it was called the C103 connector. It should be in all e30s before the wiring update in mid-'87(?). You should also have an idle control harness with a large green plug that was eliminated in later 1.3 versions of the Motronic system. Like others have mentioned, it must be spliced into the large motronic plug in order to make the tach functional.

I had two plugs very similar to that one on a '90 325i harness - one was white and the other was black. They didn't connect to anything. I've never know what they were for, figured it was for the stereo or some sort of OEM dealer-installable security system.

interesting, I'll have to find that.

I am using a full M42 engine harness, so the idle control wiring came out with the M10 harness.

I'll have to see if I can find the C103 - I guess that has to be spliced into the wire coming from the M42's C101 connector (black wire), since the M10 C101 doesn't have a pin for tach.